Motor fuel composition



United States Patent C) This invention relates to a motor fuel composition containing a novel anti-knock additive. More particularly, the invention relates to a motor fuel for spark ignition, internal combustion engines containing a salt of selenic acid and a nitrogen-containing hydrocarbyl amine or Schitf base compound as an anti-knock agent.

Present day internal combustion engines have high compression ratios and require high octane fuels for satisfactory performance. This places a severe strain on petroleum refiners to produce fuels having the necessary high octane ratings demanded by these engines. The trend to higher octane ratings is continuing and it is estimated that motor fuels having octane ratings of the order of 105 and above will be required in the foreseeable future.

At the present time, premium motor fuels having octane ratings of 97 and above are generally provided by relying heavily on one or more refining operations, such as fluid catalytic cracking, catalytic reforming, alkylation and isomerization, in conjunction with the use of a conventional anti-knock additive, such as a tetraalkyl lead compound. Frequently, these steps are not satisfactory to efficiently or economically produce a high octane motor fuel. As a result, many proposals have been made directed to fuel compositions containing useful additives, such as octane appreciators and the like, to supplement or increase the anti-knock property of present day high performance motor fuels.

The present invention involves the discovery that a gasoline or motor fuel can be substantially improved with respect to its anti-knock property by the use of 0.01 to 5 weight percent of a salt formed from selenic acid and a nitrogen-containing hydrocarbyl amine or Schiff base compound described hereinbelow. These salts are true anti-knock agents as evidenced by the fact that they will substantially improve the octane rating of a motor fuel in the absence of the conventional tetraethyl lead anti-l nock additive.

The anti-knock salts of selenic acid and of a nitrogencontaining compound of the invention are represented by one of the following formulas:

(a) H SeO (RNR'R x (b) I-I SeO (RN=CHR") in which R is a hydrocarbyl radical having from 3 to 24 carbon atoms, R is hydrogen or an alkyl radical having from 1 to 18 carbon atoms and x is an integer from 1 to 2.

"ice

Nitrogen-containing compounds which can be employed to prepare the salts of selenic acid include the hydrocarbyl amines, and in particular the hydrocarbyl primary amines, in which the hydrocarbyl radical has from 3 to 24 carbon atoms. The hydrocarbyl radical can be an alkyl radical of the indicated chain length or an aryl radical having from 6 to 24 carbon atoms. Specific amines which can be employed are t-butylamine, t-octylamine, oleylamine, cyclohexylamine, caprylylamine, dicyclohexylamine, dibutylamine, tributylamine, di-2-e-thylhexylamine, nonylamine, dodecylamine, tetradecylamine, hexadecylamine, octadecylamine, docosylamine, aniline, naphthylamine and mixtures of the foregoing amines. The preferred amines are the primary alkyl'amines in which the alkyl radical has from 8 to 24 carbon atoms. Particularly valuable amines for preparing the salt of the invention are certain commercially available mixtures of tertiary alkyl amines, namely Primene 8l-R and Primene JM-T. Primene 8l-R is a mixture of tertiary C primary aliphatic amines and Primene IM-T is a mixture of tertiary C primary aliphatic amines.

Other nitrogen-containing compounds which can be employed to prepare the salts of the invention are certain Schiff bases. The effective Schiff bases are complexes resulting from the reaction of a mole each of a primary amine and an aldehyde in which a mole of water is split out. They are prepared by reacting a primary amine, such as one of the above-noted primary amines, with an aldehyde under conventional conditions to produce the Schitf base. Aldehydes suitable for Schifi bases which form effective salts of the invention include formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, 2-ethylhexaldehyde, nonaldehyde and palmitic aldehyde. In general, the Schiif bases are represented by the formula:

RN: CHR' wherein R is a hydrocarbyl radical having 3 to 24 carbon atoms and R' is hydrogen or an alkyl radical having from 1 to 18 carbon atoms. The preferred Schiff bases are those in which R is a radical having from 8 to 24 carbon atoms and R is hydrogen or an alkyl radical having from 1 to 8 carbon atoms.

The anti-knock additive of this invention is readily prepared by mixing selenic acid with a nitrogen containing compound disclosed hereinabove. One to two moles of the nitrogen-containing compound are generally combined with one mole of selenic acid to form an effective salt although an excess of the nitrogen-containing compound over 2 moles can be employed to promote an improvement in the solubility of the salt. It is generally preferred, however, to combine the acid and the nitrogen-containing compound in 1:1 mole proportions.

Outstandingly effective salts of the invention are produced from the following mixtures of selenic acid and nitrogen-containing compound. The Schiff bases in the following salts represent the reaction produce of a mole of Primene JM-T and a mole of formaldehyde.

1 mole of selenic acidzl mole Primene JM-T 1 mole of selenic acid:2 moles Primene IMT 1 mole of selenic acid:2 moles di-Z-ethylhexylamine 1 mole of selenic acid:2 moles tricaprylylamine g 3 1 mole of selenic acidzl mole Schiif base 1 mole of selenic acidzl mole dodecylamine 1 mole of selenic acid:2 moles dodecylamine 1 mole of selenic acid:1 mole Primene 8l-R 1 mole of selenic acid:2 moles Primene 8l-R 1 mole of selenic acidzl mole docosylamine .and 3.0 volume percent being preferred. The hydrocarbon fraction of the fuel will generally contain aromatic and/or olefinic components in addition to the parafiins ordinarily present in a motor fuel. The aliphatic and/ or olefinic component can constitute as high as 100 percent of the fuel but usually will amount to between about .20 and 80 volume percent of the fuel.

As noted above, the salts of the invention are true .anti-knock agents since they substantially improve the octane rating of the fuel in the absence of any other antiknock agent. invention is that organo-lead anti-knock agents can be employed together with a salt of the invention to produce a motor fuel composition having an unusually enhanced octane rating. The organo-lead additives generally employed for anti-knockpurposes in motor fuels are the tetraalkyl lead compound. Typical tetraalkyl lead compound are tetraethyl lead, tetramethyl lead and mixtures thereof. The tetraethyl lead mixture commercially available for automotive use also contains an ethylene bromide-ethylene chloride scavenger for removing lead from the combustion chamber in the form of, volatile lead halides, the latter two reagents being present'in 1.0 theory and 0.5 theory respectively, theory denoting the stoichiometric amount required for reaction with the lead content of the tetraethyl lead. The commercial tetraalkyl lead compositions containing a lead scavenger are referred to herein as tetraalkyl lead fluids.

The tetraalkyl lead fluid is employed in motor fuel compositions in concentrations between 0.5 ml. per gallon up to the statutory limit of organo-lead reagent concentrations, which at the present time is 4 ml. per gallon for automotive fuel. The usual concentration of the tetraethyl lead fluid employed is between 1 and 3 ml. per gallon of gasoline.

The improvement in motor fuels containing saltsof selenic acid and of a nitrogen-containing compound was demonstrated by incorporating measured amounts of these salts in various fuel compositions and determining the incremental increase in octane number. In these tests, the octane number was determined by the research octane method. Three different fuels having the following compositions were employed in the tests:

Fuel A was .a premium grade gasoline having a Research Octane Rating of 94.3 and boiling in the range from 88 F. to 368 F. This fuel contained no conventional tetraalkyl lead anti-knock agent.

Test Fuel B was a premium grade gasoline similar to Test Fuel A except that it contained. 3 cc. of tetraethyl lead per gallon. With the tetraethyl lead, this fuel had an R.O.N. value of 99.6

Test Fuel C was a regular grade gasoline having a Research Octane Rating of 86.3 boiling in the range of 96 F. to 383 F. This gasoline contained no conventional tetraalkyl lead anti-knock agent.

The additive salts of the invention were incorporated in the foregoing fuels and the incremental increase in R.O.N. value was determined by running the fuels in a However, an important feature of this 4 i conventional CFR engine test. The test results are given in Table I below:

Table l Selenie Acid Salt and Wt. Mole Motor Fuel Increase Percent in Fuel Ratio R.0.N.

{Unleaded Premium Fuel A 1.0 5. 7 7.8 1:2 do 2.3 amine 2.15. Hgsgolzlfrieaprylylamine 1:2 d0 3. 0 HzSeOnSehifi Base 1.6 1:1 do 3.4 HzSeOuTrieaprylylamiue 1:2 Premium Fuel B 2. 6

3.0. with 3 ceJgal.

TEL. HzSeOnSchitf Base 1 1.6 1:1 do 1. 7

HzSeOu Di-2-ethylhexylamine:

regular.

. .do i

1 Sehiff Base formed by reaction of 0184; primary aliphatic amines and formaldehyde.

3. 0 HzSGO4ISOl1lfi Base The foregoing tests show that minor amounts of salts of selenic acid and of a nitrogen-containing compound are highly effective anti-knock additives in a variety of motor fuel compositions. Appropriate amounts of the salts of the invention can raise the R.O.N. value of a motor fuel about 8 points or more which gives petroleum refiners another method for providing super premium motor fuels. It is understood that the gasoline of the invention can contain conventional motor fuel additives, such as anti-icing, anti-stalling agents, stabilizers, corrosion and deposit inhibitors and the like.

Obviously, many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and, therefore, only such limitations should be imposed as are indicated in the appended claims.

We claim:

, 1. A motor fuel comprising hydrocarbons in the gasoline boiling range and an effective anti-knock amount of a salt of selenic acid and of a nitrogen-containing compound selected from the group consisting of:

in which R represents a hydrocarbyl radical having from 3 to 24 carbon atoms, R and R" each represent a radical selected from the group consisting of hydrogen and a hydrocarbyl radical having from 1 to 18 carbon atoms and x is an integer from 1 to 2, and

in which R is a hydrocarbyl radical having from 3 to 24 carbon atoms, R represents a radical selected from the group consisting of hydrogen and an alkyl radical having from 1 to 18 carbon atomsand x is an integer from 1 to 2. a

2. A motor fuel according to claim 1 in which said anti-knock additive amounts to 0.01 to 5 weight percent of said fuel.

3. A motor fuel according to claim 1 in which said nitrogen-containing compound is a hydrocarbyl primary amine in which the hydrocarbyl radical has from 3 to 24 carbon atoms.

4. A motor fuel accordingto claim 1 inwhich the molar ratio of said selenic acid to said nitrogen-containing compound is 1:1.

5. A motor fuel according to claim 1 in which said salt consists of a mole of selenic acid and 2 moles of di-Z-ethylhexylamine. Y

6. A motor fuel according to claim 1 in which said salt consists of a mole of selenic acid and a mole of tricaprylylamine.

7. A motor fuel according to claim 1 in which said salt consists of a mole of selenic acid and 2 moles of a mixture of tertiary C1342 primary aliphatic amines.

S. A motor fuel according to claim 1 in which said salt consists of a mole of selenic acid and a mole of a Schiif base formed from an equimolar mixture of tertiary C primary aliphatic amines and formaldehyde.

9. A motor fuel according to claim 1 containing from 0.5 ml. to 4 ml. of a tetraalkyl lead fluid.

10. A motor fuel comprising hydrocarbons in the gasoline boiling range and 0.10 to 3.0 volume percent of a salt of selenic acid and a primary alkyl amine having the formula:

Reterences (Zited by the Examiner UNITED STATES PATENTS 1,575,436 3/26 Midgley 44-76 1,906,724 5/ 33 Rosenstein et al. 44-76 1,920,766 8/33 R-osenstein et al 44-76 2,151,432 3/39 Lyon et a1 4469 DANIEL E. WYMAN, Primary Examiner. 5 

1. A MOTOR FUEL COMPRISING HYDROCARBONS IN THE GASOLINE BOILING RANGE AND AN EFFECTIVE ANIT-KNOCK AMOUNT OF A SALT OF SELENIC ACID AND OF A NITROGEN-CONTAINING COMPOUND SELECTED FROM THE GROUP CONSISTING OF: 